Environmental Monitoring - Part 4 pot

371 Uranium, Thorium, and Potassium in Soils along the Shore of Lake Issyk-Kyol in the Kyrghyz Republic* D.M. Hamby and A.K. Tynybekov CONTENTS 15.1 Introduction 371 15.2 Methods 372 15.2.1 Sample Collection 372 15.2.2 Sample Counting 373 15.2.3 Calculation of Elemental Concentrations 373 15.3 Results and Conclusions 374 Acknowledgment 376 References 376 15.1 INTRODUCTION Lake Issyk-Kyol is situated in the northeast region of Kyrghyzstan, one of the independent republics of the former Soviet Union and bordered by China to the south and east, Kazakstan to the north, and Uzbekistan and Tajikistan to the west of 6240 km 2 and a depth of 668 m. It lies in the valley between the Terskei mountains to the north and the Kungei mountains to the south, at a surface elevation of 1550 m (CAGC, 1987). The briny lake, fed by mountain runoff which flows through about 80 small rivers and creeks, has no discharge streams. Lake Issyk-Kyol is used for swimming, boating, and fishing, but because of its salt content, it is not a direct source of drinking water. During the Soviet era, hotels along the central northern shore of Lake Issyk-Kyol were well-known vacation spots for the Soviet elite, but * From Hamby, D. 2002. Environmental Monitoring and Assessment, 73(2): 101–108. Reprinted with permission by Kluwer Publ. 15 L1641_Frame_C15.fm Page 371 Tuesday, March 23, 2004 7:36 PM © 2004 by CRC Press LLC (Figure 15.1). The lake is one of the largest in Central Asia, having a surface area 372 Environmental Monitoring otherwise it remained in virtual isolation from the outside world until the early 1990s. Today, the lake attracts tourists from all over Central Asia. A government commission in Kyrghyzstan was established from 1994 to 1996 to assess the radiation situation at Lake Issyk-Kyol and determine whether radioactivity in areas with elevated radiation levels was natural or man-made. An investigation of radiation levels along the shoreline of Lake Issyk-Kyol was conducted previously by Kyrghyz scientists (SCSC, 1990) and more recently by Hamby and Tynybekov (1999). The SCSC (1990) survey included about 400 measurements and our survey consisted of over 2200 measurements taken along the perimeter of the lake. The most recent measurements indicate that sampling locations near Genish, Kadji-Sai, Bokonbaevo, and Cholpon-Ata have radiation exposure rates in excess of ten times ambient levels (Hamby and Tynybekov, 1999). To corroborate earlier data and to determine the source of the increased radiation fields, a radiological assessment of the shoreline of Lake Issyk-Kyol was executed, including analyses of nearly 300 soil samples. We have measured concentrations of thorium, uranium, and potassium in the shoreline soils. Each of these naturally occurring elements has isotopes that are radioactive and may increase the amount of exposure received by the populations living in the vicinity of the lake. These exposures can result in individuals receiving radiation dose in the form of external gamma radiation or internal alpha and beta emissions. Additionally, radon is a decay progeny of thorium and uranium and may result in increased radiation dose via the inhalation exposure pathway. The following study reports on the results of our soil analyses at Lake Issyk-Kyol. 15.2 METHODS 15.2.1 S AMPLE C OLLECTION In early 1999, several hundred soil samples were obtained from 99 locations around the shoreline of Lake Issyk-Kyol. The selection of these sampling locations was driven by results from previous assessments of external exposure rates in the region FIGURE 15.1 Location in Central Asia of the Kyrghyz Republic and Lake Issyk-Kyol. (From Hamby, D.M. and Tynbekov, A.K. 2002. Environ Monitor. Assess ., 73: 101–108. With permission.) L1641_Frame_C15.fm Page 372 Tuesday, March 23, 2004 7:36 PM © 2004 by CRC Press LLC Uranium, Thorium, and Potassium in Soils along the Shore of Lake 373 (Hamby and Tynybekov, 1999), so as to include representative areas of both high and low gamma exposure. Samples were collected at locations near the mouths of streams emptying into Lake Issyk-Kyol, along the shoreline of the lake, and at specific locations with elevated radiation levels. Precise positional data were recorded using a portable GPS receiver. Soil samples were collected by first recording the location and relative exposure rate at 1 m from the undisturbed surface directly over the area to be sampled. An area of 30 × 30 cm was marked and cleared of debris. Three 30 to 40 g samples (wet weight) of surface soil to a depth of 1 to 2 cm were collected at random within the marked 900 cm 2 area. The three samples were then combined into one, sifted, mixed thoroughly, and dried for 4 h in a 100 ° C oven. Water fractions averaged 8.9%, ranging from less than 1% to as much as 37%. Dry weights of combined samples were consequently 83.6 ± 12.1 g. Dried samples were sealed in 250 ml polyurethane bottles and set aside for a minimum of 30 d to allow the in-growth of uranium and thorium decay products (Myrick et al., 1983; Murith et al., 1986). 15.2.2 S AMPLE C OUNTING Prepared soil samples in radiological equilibrium were counted in their sealed bottles on a high-purity germanium (HPGe) detector with 70% efficiency, relative to a 3 × 3" NaI. Following a 30-min counting time, count rates were recorded for five gamma energies: 0.239 MeV ( 212 Pb, with a 44.6% gamma yield); 0.352 MeV ( 214 Pb, 37.1%); 0.609 MeV ( 214 Bi, 46.1%); 0.911 MeV ( 228 Ac, 27.7%); and 1.461 MeV ( 40 K, 10.7%). Concentrations of 232 Th were determined from the average concentrations of 212 Pb and 228 Ac in the samples, and 238 U was determined from the average of the 214 Pb and 214 Bi concentrations. Radiological concentrations of 232 Th, 238 U, and 40 K were then converted to total elemental concentrations of thorium, uranium, and potassium in surface soils, as described in the following text. Total thorium and uranium concentrations are reported in units of ppm, while concentrations of potassium are reported in units of percent. 15.2.3 C ALCULATION OF E LEMENTAL C ONCENTRATIONS Radiological concentrations in soils collected from the Issyk-Kyol shoreline are deter- mined from measurements of the gamma rays emitted by specific radionuclides in the decay of uranium, thorium, and potassium. These concentrations, while specific only to particular radioisotopes, are used to estimate elemental concentrations in the soil samples. Since the decay progeny of 232 Th and 238 U are measured, we must rely on the establishment of secular equilibrium in the samples in order to provide an accurate measurement of total thorium and uranium, hence the 30-d in-growth time. A true measure of potassium is taking place since we are measuring 40 K directly. Elemental concentrations are calculated from measured radiological concentra- tions in the soil samples. First, the radiological concentration of nuclide i, C S,i, in units of Bq per gram of soil, is calculated using C C Y M Si ii x , ˙ = ⋅⋅ε L1641_Frame_C15.fm Page 373 Tuesday, March 23, 2004 7:36 PM © 2004 by CRC Press LLC 374 Environmental Monitoring where is the measured count rate (cts/sec), Y i is the yield of gamma rays per disintegration, ε i is the efficiency (cts/gamma) of the detector at the energy of the nuclide i gamma ray, and M x is the dry mass of the soil sample being analyzed. The fraction of the element in the soil sample, F E , in units of percent or ppm, is then calculated by where M A,j is the atomic mass (g/mol) of element j; λ i is the decay constant (s − 1 ) of the radioisotope being counted; N A is Avogadro’s number (6.022 × 10 23 atom/mol); f A,i is the fractional atomic abundance of 232 Th, 238 U, or 40 K; and the constant, K (with a value of 100 or 1,000,000), converts the ratio of the element’s mass to soil mass into a percentage or ppm. 15.3 RESULTS AND CONCLUSIONS Concentrations of total thorium, uranium, and potassium are plotted in Figure 15.2 for our 99 sampling locations around the perimeter of Lake Issyk-Kyol. Measured concen- trations over all sampling sites are 53 ± 110 ppm, 21 ± 64 ppm, and 5.7 ± 1.3% for thorium, uranium, and potassium, respectively. For comparison, Myrick et al. (1983) FIGURE 15.2 Thorium, uranium, and potassium concentrations in soils on the shore of Lake Issyk-Kyol. (From Hamby, D.M., and Tynbekov, A.K. 2002. Environ Monitor. Assess ., 73: 101–108. With permission.) ˙ C i F CM Nf K Ej Si A j iAAi , ,, , = ⋅ ⋅⋅ ⋅ λ 1 10 100 1000 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 Location Identifier Thorium and Uranium Concentration (ppm) 1 10 100 1000 Potassium Concentration (%) Thorium Uranium Potassium L1641_Frame_C15.fm Page 374 Tuesday, March 23, 2004 7:36 PM © 2004 by CRC Press LLC Uranium, Thorium, and Potassium in Soils along the Shore of Lake 375 have determined arithmetic mean concentrations and standard deviations of tho- rium and uranium in surface soils in more than 300 samples obtained from locations around the U.S. to be 8.9 ± 4.2 ppm and 3.0 ± 2.5 ppm, respectively. Also, Chang et al. (1974) report the concentrations of thorium, uranium, and potassium in earthen building materials of Taiwan to range from 14 to 16 ppm, 1.2 to 4.3 ppm, and 0.15 to 12.8%, respectively. Potassium concentrations in a wide variety of rock types are estimated to range from approximately 0.1 to 3.5% (Kohman and Saito, 1954). For thorium at Lake Issyk-Kyol, if the two high concentrations at locations 37 remaining soil samples is 37 ± 20 ppm, about a factor of two-to-four greater than the averages of Myrick et al. (1983) and Chang et al. (1974). Likewise, removing the four high concentrations at locations 87, 90, 95, and 96, the concentration of uranium is 10 ± 5 ppm, a factor of about three greater. An analysis of concentrations of potassium in Lake Issyk-Kyol shoreline soils shows less variability among samples, with two comparatively low values being recorded for locations 28 and 38. If these values are removed from the analysis, the concentration of potassium in the Issyk-Kyol shoreline is 5.8 ± 1.1%, in the range of the data of Chang et al. (1974), but about 65% higher than Kohman and Saito’s (1954) high value. Several representative sampling points plotted relative to the lake’s shoreline are shown in Figure 15.3. These particular locations are plotted to highlight areas found to have elevated radiation exposure rates (Hamby and Tynybekov, 1999) and areas FIGURE 15.3 Relative radiation levels and areas of relatively high thorium, uranium, and potassium concentrations at specific locations on the shoreline of Lake Issyk-Kyol. (From Hamby, D.M., and Tynbekov, A.K. 2002. Environ Monitor. Assess ., 73: 101–108. With permission.) 78.0 77.0 76.076.0 42.0 42.2 42.4 42.6 43.0 Lake Shore Exposure ~ bkg Exposure 1-3 bkg Exposure > 3 bkg Thorium > 45 ppm Uranium > 100 ppm Potassium > 6.5 % Population Center Cholpon-Ata Balykchy Bokonbaevo Kadji-Sai Genish Kyzyl-Suu Karakol Tup Degrees Longitude (E) Degrees Latitude (N) L1641_Frame_C15.fm Page 375 Tuesday, March 23, 2004 7:36 PM © 2004 by CRC Press LLC and 38 (Figure 15.2) are removed from the analysis, the concentration over the 376 Environmental Monitoring of relatively high uranium, thorium, and potassium concentrations. As expected, locations with high soil concentrations of these radionuclides (locations 37, 38, 87, 90, 95, and 96) are consistently located near areas of the lake previously determined to have high exposure-rate measurements (SCSC, 1990; Karpachov, 1996; Hamby and Tynybekov, 1999). Measurements by our international team of scientists have confirmed the exist- ence of areas with elevated levels of radiation exposure and high concentrations of naturally occurring radionuclides on the southern shore of Lake Issyk-Kyol. Tho- rium, uranium, and potassium concentrations in specific areas near the lake are somewhat higher than average concentrations around the world. Visual inspection of Lake Issyk-Kyol’s white, sandy beaches near the towns of Bokonbaevo and Kadji- Sai show a distinctive mixture of black sands in very localized areas. Monazite is an insoluble rare-earth mineral that is known to appear with the mineral ilmenite in sands at other locations in the world (Eisenbud, 1987). Monazite contains primarily radionuclides from the 232 Th series, and also contains radionuclides in the 238 U series. The sands on the Lake Issyk-Kyol beaches very likely contain monazite and ilmenite. These mineral outcroppings are the source of radioactivity along the shoreline of Lake Issyk-Kyol. Historical evidence provides insight into possible other sources of radioactivity in this area of the world; however, our results suggest that shoreline radioactivity is of natural origins. ACKNOWLEDGMENT This work was conducted with partial financial support from the U.S. Civilian Research and Development Foundation (Grant No. YB1-121) and the NATO Science Program and Cooperation Partners (Linkage Grant No. 960619). REFERENCES Chang, T.Y., Cheng, W.L., and Weng, P.S. 1974. Potassium, uranium and thorium content in building material of Taiwan. Health Phys. , 27(4): 385–387. Chief Administration of Geodesy and Cartography (CAGC). 1987. Atlas of the Kyrghyz Soviet Socialist Republic. Natural conditions and resources. Vol. 1. Moscow (in Russian). Eisenbud, M. 1987. Environmental Radioactivity: From Natural, Industrial, and Military Sources . 3rd ed., Academic Press, New York. Hamby, D.M. and Tynybekov, A.K. 1999. A screening assessment of external radiation levels on the shore of lake Issyk-Kyol in the Kyrghyz Republic. Health Phys ., 77(4): 427–430. Hamby, D.M. and Tynybekov, A.K. 2002. Uranium, thorium, and potassium in soils along the shore of Lake Issyk-Kyol in the Kyrghyz Republic, Environ. Monitor. Assess ., 73: 101–108. Karpachov, B.M. 1996. Regional radiological investigations in the Kyrghyz Republic. In: Proceedings of the 1st Conference on Prospective Planning for Continued Ecological Investigations in the Kyrghyz Republic (translated), pp. 14–15. Bishkek, Kyrghyzstan (in Russian). L1641_Frame_C15.fm Page 376 Tuesday, March 23, 2004 7:36 PM © 2004 by CRC Press LLC Uranium, Thorium, and Potassium in Soils along the Shore of Lake 377 Kohman, T. and Saito, N. 1954. Radioactivity in geology and cosmology. Annu. Rev. Nucl. Sci. , 4. Murith, C., Voelkle, H., and Huber, O. 1986. Radioactivity measurements in the vicinity of Swiss nuclear power plants. Nucl. Instrum. Methods , A243: 549–560. Myrick, T.E., Berven, B.A., and Haywood, F.F. 1983. Determination of concentrations of selected radionuclides in surface soil in the U.S. Health Phys ., 45(3): 631–642. SCSC. 1990. Radiation Investigation of Lake Issyk-Kyol. Issyk-Kyol Ecology Branch of the State Committee Scientific Center for the Kyrghyz Republic and the Issyk-Kyol Station of Chemistry Planning and Investigation (SCSC). 1990. Bishkek, Kyrghyzstan (in Russian). L1641_Frame_C15.fm Page 377 Tuesday, March 23, 2004 7:36 PM © 2004 by CRC Press LLC 379 Monitoring and Assessment of the Fate and Transport of Contaminants at a Superfund Site K.T. Valsaraj and W.D. Constant CONTENTS 16.1 Introduction 379 16.2 Assessment of Chemodynamic Data for Field Soils 381 16.2.1 Equilibrium Desorption from Soil 381 16.2.2 Kinetics of Desorption from Soil 382 16.2.3 Bioavailability of the Tightly Bound Fraction in the Soil 384 16.3 Implications for Site Remediation 386 Acknowledgments 388 References 389 16.1 INTRODUCTION Contamination of soils poses a serious environmental problem in the U.S. The Comprehensive Environmental Response Compensation and Liability Act (CER- CLA) of 1980 established the so-called Superfund provisions whereby a trust fund was set up to provide for cleanup of hundreds of abandoned hazardous waste sites. Several of these sites were put on the National Priorities List (NPL) and slated for cleanup. Two such sites are located north of Baton Rouge in Louisiana in the U.S. Environmental Protection Agency (EPA) Region 6 and are called the Petro Proces- sors, Inc. (PPI) sites. PPI sites comprise two former petrochemical disposal areas situated about 1.5 miles apart near Scotlandville, about 10 miles north of Baton Rouge, the Scenic Highway, and Brooklawn sites, totaling 77 acres. Brooklawn is the larger of the two areas, currently estimated at 60 acres. These sites were operated in the late 1960s and early 1970s to accept petrochemical wastes. During their operation, 16 L1641_Frame_C16.fm Page 379 Tuesday, March 23, 2004 7:37 PM © 2004 by CRC Press LLC 380 Environmental Monitoring approximately 3.2 × 10 5 tons of refinery and petrochemical wastes were disposed in nonengineered pits on the two sites. Free phase organics are present in buried pits and high permeability soil lenses are found in the proximity of the disposal area. A concerted effort was made in the early 1980s through soil borings and drilling wells to determine the types and nature of contaminants at the site. Table 16.1 lists the major contaminants found at the site. Contaminants at the sites are predominantly chlorinated organic solvents and aromatic hydrocarbons. A conventional hydraulic containment and recovery system, pump-and-treat (P&T), was initiated in 1989 with a plan for a total of 214 wells at the bigger Brooklawn site. However, this method was shown to require unrealistically long times to make significant reductions in the quantity of organic contaminants. 1 This was primarily attributed to the fact that the removal of hydrophobic organic compounds TABLE 16.1 Principal Organic and Inorganic Contaminants at the PPI Superfund Site Volatile Organic Compounds Vinyl chloride 1,1-Dichloroethene Chloroform Benzene 1,2-Dichloroethane Trichloroethene 1,2-Dichloropropane Toluene Tetrachloroethene 1,1,2-Trichloroethane Chlorobenzene Ethylbenzene 1,1,2,2-Tetrachloroethane 1,2-Dichlorobenzene 1,3-Dichlorobenzene 1,1,1-Trichloroethane Semivolatile/Base Neutrals Naphthalene Hexachlorobutadiene Hexachlorobenzene Diethylphthalate Bis-chloroethyl ether Chloro-1-propyl ether Hexachloroethane Isophorone 1,2,4-Trichlorobenzene 2,4-Dinitrotoluene Fluorene Phenanthrene Anthracene Metals Copper Zinc Cadmium Lead Chromium Nickel L1641_Frame_C16.fm Page 380 Tuesday, March 23, 2004 7:37 PM © 2004 by CRC Press LLC Monitoring and Assessment of the Fate 381 (HOCs) from contaminated soils is usually hindered by very low solubility in water. Thus, there was a need for alternative technologies or other methods to enhance the recovery of contaminants. The use of surfactants to enhance the performance of the existing well facilities was suggested, since the P&T wells were already in produc- tion, and any additional wells and equipment necessary could easily be incorporated into the system. However, one potential problem that the researchers and the regu- lators were concerned about was the possibility of downward migration of mobilized contaminants and surfactants into deeper depths of the pristine subsurface soils. Our research project, which was initiated to support the groundwater geochem- ical model, MODFLOW ® , yielded interesting findings. We observed that a significant fraction of the contaminant was irreversibly bound to the soil. A measure of the desorption-resistant fraction and its bioavailability was not readily available. To fill this knowledge gap, a comprehensive study on the sorption/desorption hysteresis, desorption kinetics, and bioavailability of key contaminants was undertaken. The findings of these studies along with other supporting data eventually resulted in the selection of monitored natural attenuation (MNA) as the current remediation scheme now in place for the two sites. This chapter details the results of our environmental chemodynamic studies at the site. The discussion is selective in that only the chemo- dynamic data for two of the several contaminants are considered for this chapter as illustrations. 16.2 ASSESSMENT OF CHEMODYNAMIC DATA FOR FIELD SOILS Fate, transport, and risk assessment models require both equilibrium and kinetic data on desorption of contaminants from soil. Studies suggested a two-stage (biphasic) desorption of organic chemicals from soils and sediments. A rapid release of a loosely bound fraction is followed by the slow release of a tightly bound fraction. 2–4 Quantitative models have been only partly successful in explaining desorption hys- teresis, irreversibility, and slowly reversible, nonequilibrium behavior. The bioavail- ability of a chemical is also controlled by a number of physical–chemical processes such as sorption and desorption, diffusion, and dissolution. 5,6 Several researchers have confirmed that biodegradation can be limited by the slow desorption of organic compounds. 7–10 Long-term persistence in soils of intrinsically biodegradable com- pounds in field contaminated (aged) soil has also been noted. 2,11 16.2.1 E QUILIBRIUM D ESORPTION FROM S OIL To test the above hypothesis, we conducted an experiment using field-contaminated soil from the PPI sites. Though the tests involved several chlorinated organics the discussion here is limited to HCBD as it is one of the most prevalent compounds present at high concentrations throughout the site. The soil was subjected to sequential desorption using distilled water and the aqueous concentration after each desorption step was obtained. 12 The initial concentration in water in equilibrium with the soil was 2120 ± 114 µ g/l and declined to about 1200 µ g/l after 20 desorption steps (140 d). The mass L1641_Frame_C16.fm Page 381 Tuesday, March 23, 2004 7:37 PM © 2004 by CRC Press LLC [...]... Environ Stat 7: 45 2 46 8 2002 © 20 04 by CRC Press LLC L1 641 _C17.fm Page 40 6 Tuesday, March 23, 20 04 8:59 PM 40 6 Environmental Monitoring 83 Cox, L H Statistical issues in the study of air pollution involving airborne particulate matter Environmetrics 11: 611–626, 2000 84 Gregoire, T G Design-based and model-based inference in survey sampling: appreciating the difference Can J For Res 28: 142 9– 144 7, 1998 85... Monit Assess 51: 89–106, 1998 © 20 04 by CRC Press LLC L1 641 _C17.fm Page 40 4 Tuesday, March 23, 20 04 8:59 PM 40 4 Environmental Monitoring 40 Smith, W F ANOVA-like similarity analysis using expected species shared Biometrics 45 : 873–881, 1989 41 Solow, A R Detecting changes in the composition of a multispecies community Biometrics 50: 556–565, 19 94 42 Zangerl, A R., McKenna, D., Wraight, C L., Carroll,... Network Y.-P Lin CONTENTS 18.1 18.2 Introduction 40 7 Multiple-Point Variance Analysis (MPV) 40 9 18.2.1 Geostatistics .40 9 18.2.2 Multiple-Point Variance Reduction Analysis (MPVR) .41 0 18.2.3 Multiple-Point Variance Increase Analysis (MPVI) 41 3 18.2 .4 Optimal MPVR and MPVI 41 4 18.3 Case Study of an Optimal Adjustment 41 7 18.3.1 MPVR and MPVI Applications 41 8... Information Efficiency 42 1 18.3.3 Combined Optimal MPVI and MPVR .42 1 18 .4 Summary and Conclusion 42 4 References 42 4 18.1 INTRODUCTION Designing an environmental monitoring network involves selecting sampling sites and frequencies.1 However, an optimal information-effective monitoring network should provide sufficient but no redundant information of monitoring variables The... here, data for 1,3-DCB with silty soil from © 20 04 by CRC Press LLC L1 641 _Frame_C16.fm Page 383 Tuesday, March 23, 20 04 7:37 PM Monitoring and Assessment of the Fate 383 Fraction DCB remaining in soil 1.0 3 d old 3 d old - fit 3 months old 3 months old - fit 5 months old 5 months old - fit 0.8 0.6 0 .4 0.2 0.0 0 100 200 300 40 0 500 600 time/h FIGURE 16.2 The rate of desorption of 1,3-dichlorobenzene... little used in most environmental assessments since the major emphasis is to determine effect The design-based approaches are more used in monitoring situations in which the interest is reporting averages or totals such as might be seen in fisheries management © 20 04 by CRC Press LLC L1 641 _C17.fm Page 40 2 Tuesday, March 23, 20 04 8:59 PM 40 2 Environmental Monitoring Both assessment and monitoring are similar... 23, 20 04 8:59 PM 17 Statistical Methods for Environmental Monitoring and Assessment E Russek-Cohen and M C Christman CONTENTS 17.1 Introduction 391 17.2 Overview 392 17.3 Types of Endpoints 393 17 .4 Assessment .395 17.5 Environmental Monitoring 399 17.6 Statistical Aspects of Monitoring Air Quality: An Example 40 0 17.7 Summary 40 1 References... texts 24) These methods make © 20 04 by CRC Press LLC L1 641 _C17.fm Page 3 94 Tuesday, March 23, 20 04 8:59 PM 3 94 Environmental Monitoring fewer assumptions than parametric models Reliability engineers have also been interested in time until a component fails but have developed a number of parametric models to accommodate such data.25 Left-censored data and doubly censored data (data which can be left- or... Statistical advances in environmental science Stat Sci 13: 186–208, 1998 80 Urquhart, N S and Kincaid, T M Monitoring for policy-relevant regional trends over time Ecol Appl 8: 246 –257, 1998 81 Urquhart, N S and Kincaid, T M Designs for detecting trend from repeated surveys of ecological resources J Agric Biol Environ Stat 4: 40 4 41 4, 1999 82 Polansky, A M and Check, C E Testing trends in environmental compliance... Geostatistics, a spatial statistical technique, is widely applied to analyze environmental monitoring data in space and time Geostatistics can characterize and quantify spatial variability, perform rational interpolation, and estimate the variance 40 7 © 20 04 by CRC Press LLC L1 641 _C18.fm Page 40 8 Tuesday, March 23, 20 04 7:38 PM 40 8 Environmental Monitoring in the interpolated values Kriging, a geostatistical method, . permission.) 78.0 77.0 76.076.0 42 .0 42 .2 42 .4 42.6 43 .0 Lake Shore Exposure ~ bkg Exposure 1-3 bkg Exposure > 3 bkg Thorium > 45 ppm Uranium > 100 ppm Potassium > 6.5 % Population Center Cholpon-Ata Balykchy Bokonbaevo Kadji-Sai Genish Kyzyl-Suu Karakol Tup Degrees. j iAAi , ,, , = ⋅ ⋅⋅ ⋅ λ 1 10 100 1000 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 Location Identifier Thorium and Uranium Concentration (ppm) 1 10 100 1000 Potassium Concentration (%) Thorium Uranium Potassium . 0.239 MeV ( 212 Pb, with a 44 .6% gamma yield); 0.352 MeV ( 2 14 Pb, 37.1%); 0.609 MeV ( 2 14 Bi, 46 .1%); 0.911 MeV ( 228 Ac, 27.7%); and 1 .46 1 MeV ( 40 K, 10.7%). Concentrations